1. Field of the Invention
The present invention relates to technology for generating a reception notification signal in response to sensing of a first communication device transmitting a data signal, transmitting the generated reception notification signal to a plurality of communication devices sharing a wireless channel with the first communication device, providing notification on an occupation of the wireless channel by the first communication device to each of the communication devices, and delaying processing of a data transmission request input from a second communication device while maintaining the transmitting of the reception notification signal, thereby effectively preventing a collision between data signals transmitted through the wireless channel.
2. Description of the Related Art
In general, a method of managing wireless resources in a wireless communication system may be classified into a centralized scheme and a distributed scheme.
In the centralized scheme, the wireless communication system may use a licensed band for allocating wireless resources to a single communication device disposed in a predetermined area. A mobile communication network led by a third generation partnership project (3GPP) may be an example of the wireless communication system employing the centralized scheme. The mobile communication network may include a plurality of cell areas, and all wireless resources may be managed by a single node in each of the cell areas. Thus, a node may allocate available wireless resources to each communication device to prevent an occurrence of a collision.
However, in a wireless communication system employing a distributed wireless resources management scheme using an unlicensed band such as an industrial, scientific, and medical (ISM) band, since wireless resources are shared among communication devices, a single node may experience a difficulty in controlling allocation of wireless resources to all communication devices, which may be possible in a centralized wireless resources management scheme. Thus, in the unlicensed band, each of the communication devices may individually determine a time for using wireless resources.
In the distributed wireless resources management scheme, a probability of a wireless resources collision occurring between communication devices may be relatively high when compared to the centralized wireless resources management scheme. A wireless local area network (WLAN), for example the Institute of Electrical and Electronics Engineers (IEEE) 802.11 may be an example of a wireless communication system using the distributed wireless resources management scheme. In the WLAN, a carrier sense multiple access with commission avoidance (CSMA/CA) method may be used to reduce occurrences of wireless resources collisions between communication devices.
In the WLAN employing the CSMA/CA method, an occurrence of a collision between the communication devices may be avoided by verifying whether wireless resources are being used by another communication device before transmitting the data signal using the wireless resources, and initiating transmission of a data signal. However, in the CSMA/CA method, a hidden node issue may arise when a signal of another communication device is not verified based on a position of each communication device.
FIG. 1 illustrates a transmission and reception range of a communication device in a case of an occurrence of a hidden node issue according to a related art. FIG. 2 illustrates an example in which a hidden node issue occurs according to a related art.
Referring to FIG. 1, when a communication device A transmits a data signal to a communication device B, the data signal transmitted from the communication device A may not reach a communication device C disposed outside a transmission and reception range of the communication device A.
In this example, the communication device C may determine that a communication device transmitting a data signal is absent and thus, transmit a data signal.
Referring to FIG. 2, a hidden node issue which causes a collision due to data signals being simultaneously transmitted from a communication device A and a communication device B may occur in a communication device B. Thus, the communication device B may experience difficulty in demodulating the data signals transmitted from the communication device A and the communication device C.
To solve the hidden node issue, a scheme of using a request-to-send (RTS) signal and a clear-to-send (CTS) signal may be suggested in a related art.
FIG. 3 illustrates an example of preventing a hidden node issue using an RTS signal and a CTS signal according to a related art.
Referring to FIG. 3, in a related art, when a communication device A is to transmit a data signal to a communication device B, the aforementioned hidden node issue may be prevented by sequentially transmitting the RTS signal and the CTS signal in advance, provide notification that the communication device A is transmitting the data signal using a wireless channel to a communication device C and then, transmitting the data signal.
However, in this case, since a separate control signal such as the RTS signal and the CTS signal is transmitted along with the data signal, protocol overhead may increase.
Accordingly, there is a desire for technology to minimize protocol overhead and prevent a hidden node issue.